Exploring Electrochemical Windows of Room-Temperature Ionic Liquids: A Computational Study

Tian, Yong-Hui; Goff, George S.; Runde, Wolfgang; Batista, Enrique R.

doi:10.1021/jp303915c

Cited by 61 publications

(85 citation statements)

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“…53,54,56,57 Equations 1 and 2 imply that the LUMO and HOMO energy levels of molecules have a linear correlation with the corresponding standard reduction and oxidation potentials, respectively.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Stability of Quaternary Ammonium Cations: An Experimental and Computational Study

Mousavi

Kashefolgheta

Stein

et al. 2015

J. Electrochem. Soc.

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Quaternary ammonium ions, NR 4 + , are among the most electrochemically stable organic cations. Because of their wide electrochemical windows, they are frequently used in batteries and electrochemical capacitors. Improving the electrochemical stability and expanding the electrochemical windows of quaternary ammonium ion is highly desired. In this work, we investigated the electrochemical stability of quaternary ammonium ions and showed that the chain length, type (primary vs. secondary), size, and steric hindrance of the saturated alkyl substituents have only a very small effect (less than 150 mV) on their electrochemical stability toward reduction. To provide a molecular understanding of substituent effects on electrochemical stability, quantum calculations were performed employing density functional theory, and it was shown that the structure of saturated aliphatic alkyl substituents has only minimal effects on the electronic environment around the positive nitrogen center and the LUMO energy level of quaternary ammonium cations. Moreover, a linear correlation between the cathodic limit and the LUMO energy levels of the NR 4 + , N-butylpyridinium, and 1-ethyl-3-methylimidazolium ions was found, suggesting that electrochemical stabilities of new cations may be computationally predicted on the basis of LUMO energies of these systems. With the increasing global demand for energy, improving existing energy storage technologies is as critical as developing more efficient methods for energy production. For one important class of energy storage technologies, namely electrical energy storage, the energy density of a device is usually limited by the voltage window in which the device can function. Therefore, expanding the working voltage range of such devices is highly desired. The electrochemical decomposition of electrolytes, which are commonly used in energy storage devices such as electrochemical capacitors, often limits the useful voltage window 1 because these devices can function properly only within the electrochemical window of their electrolyte. Modifying the structure of electrolytes and improving their electrochemical stabilities has been the focus of numerous studies to date. [2][3][4][5][6][7][8][9][10][11][12][13][14][15] The electrochemical window of an electrolyte is the voltage range in which the electrolyte is chemically stable and does not get reduced or oxidized as a result of the applied potential. 16 The upper end of the electrochemical window is usually limited by the oxidation of the anion, and the lower end of the electrochemical window is determined by the reduction of the cation. 1 One of the most electrochemically stable classes of organic cations comprises the quaternary ammonium ions, NR 4 + . These are highly inert toward reduction, offer wide electrochemical windows, and are, therefore, frequently used in batteries and capacitors. 2,5,6,17 Much research has been devoted to improving the electrochemical stability of quaternary ammonium ions. 4,[9][10][11][12][13][14][15] Reduction of qua...

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Section: Resultsmentioning

confidence: 99%

Electrochemical Stability of Quaternary Ammonium Cations: An Experimental and Computational Study

Mousavi

Kashefolgheta

Stein

et al. 2015

J. Electrochem. Soc.

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“…These differences between [C 2 mIM] + and [Et 4 N] + cations can explain differences on electrochemical characteristics of electrolytes based on these salts, as it is reported in the literature that the electrochemical window of pure RTMS increases in the order of imidazolium < ammonium. 47 However, the 3D structure and charge distribution differences between selected ions ([C 2 mIM] + and [TFSI] − asymmetric structures and charges highly delocalized and [Et 4 N] + and [BF 4 ] − symmetric structures and charges highly localized) and the presence ([C 2 mIM] + cation) or the absence ([Et 4 N] + cation) of an acidic hydrogen (C 2 position on the imidazolium ring shown by the dark-blue color in the mapped surface charge distributions in Table 2) have also an impact on the cation−anion interaction in solution, as well as on the salts solvation properties in molecular solvents, which can affect the bulk properties of the ADN-based electrolytes.…”

Section: Predictive Methodsmentioning

confidence: 99%

Physicochemical Investigation of Adiponitrile-Based Electrolytes for Electrical Double Layer Capacitor

2014

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Herein, we present the formulation and the characterization of novel adiponitrile-based electrolytes as a function of the salt structure, concentration, and temperature for supercapacitor applications using activated carbon based electrode material. To drive this study two salts were selected, namely, the tetraethylammonium tetrafluoroborate and the 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide. Prior to determination of their electrochemical performance, formulated electrolytes were first characterized to quantify their thermal, volumetric, and transport properties as a function of temperature and composition. Then, cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to investigate their electrochemical properties as electrolyte for supercapacitor applications in comparison with those reported for the currently used model electrolyte based on the dissolution of 1 mol·dm −3 of tetraethylammonium tetrafluoroborate in acetonitrile. Surprisingly, excellent electrochemical performances were observed by testing adiponitrile-based electrolytes, especially those containing the 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide roomtemperature molten salt. Differences observed on electrochemical performances between the selected adiponitrile electrolytes based on high-temperature (tetraethylammonium tetrafluoroborate) and the room-temperature (1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide) molten salts are mainly driven by the salt solubility in adiponitrile, as well as by the charge and the structure of each involved species. Furthermore, in comparison with classical electrolytes, the selected adiponitrile +1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide solution exhibits almost similar specific capacitances and lower equivalent serial resistance. These results demonstrate in fact that the adiponitrile +1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide mixture can be used for the formulation of safer electrolytes presenting a very low vapor pressure even at high temperatures to design acetonitrile-free supercapacitor devices with comparable performances.

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“…Other recent applications, the (necessarily limited and biased) following selection tries only to show the wide and rich range of systems being currently afforded, include the modelling of ionic liquids [175], gas adsorption in metalorganic frameworks [176,177], isomerism in monosaccharides [178], conformational analysis [179,180], nonlinear optical responses [181], magnetic couplings in organometallics [182], enzymatic catalysis [183,184], electron paramagnetic resonance hyperfine coupling tensors [185], inclusion complexes and nanoencapsulation [186], electronic circular dichroism [187], organometallic complexes of graphene [188], interfacial chemistry [189], photosynthetic water oxidation [190], hyperpolarizability of pushpull systems [191], lightharvesting complexes [192], adsorbate-zeolite interactions [193], or harmonic and anharmonic vibrational frequency calculations [194], among others. • Figure 1.…”

Section: Self-interaction Errormentioning

confidence: 99%

Double-hybrid density functionals: merging wavefunction and density approaches to get the best of both worlds

Sancho‐García

Adamo

2013

Phys. Chem. Chem. Phys.

109

108

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We review in this Perspective why and how double-hybrid density functionals have become new leading actors in the field of computational chemistry, thanks to the combination of an unprecedented accuracy together with large robustness and reliability. Similarly to their predecessors, the widely employed hybrid density functionals, they are rooted on the Adiabatic Connection Method from which they emerge in a natural way. We present recent achievements concerning applications to chemical systems of the most interest, and current extensions to deal with challenging issues such as non-covalent interactions and excitation energies. These promising methods, despite a slightly higher computational cost than other typical density-based models, are called to play a key role in the near future and can thus pave the way towards new discoveries or advances.2

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Exploring Electrochemical Windows of Room-Temperature Ionic Liquids: A Computational Study

Cited by 61 publications

References 50 publications

Electrochemical Stability of Quaternary Ammonium Cations: An Experimental and Computational Study

Electrochemical Stability of Quaternary Ammonium Cations: An Experimental and Computational Study

Physicochemical Investigation of Adiponitrile-Based Electrolytes for Electrical Double Layer Capacitor

Double-hybrid density functionals: merging wavefunction and density approaches to get the best of both worlds

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